The present invention relates to a powder metal helical gear, a gear assembly including a powder metal helical gear, and a method of making the powder metal helical gear.
It is known to form helical gear teeth on a powder metal gear during the powder metal compaction process. There is a practical limit on the helix angle of gear teeth formed in this manner, because the powder metal is not yet sintered. If the helix angle is small, such as a few degrees, then the compacted powder metal gear blank can be withdrawn from the die by rotating the gear blank about its axis while pulling axially. However, if the helix angle is large, such as above about 27-30 degrees, then the axial force on the gear teeth caused by this pulling damages or breaks the gear teeth.
Accordingly, it is not feasible to make helical gears with a helix angle of 35.degree. or more by powder metal compaction. Such gears are typically made by machining. Machining a 35.degree. helical gear tooth form is, however, significantly more expensive than powder metal formation. Also, if the machined gear includes an integrally formed shaft or a shaft-receiving cavity, as is necessary for a pinion gear, then the machining process becomes very complex and even more expensive.